Hydrocarbon composition useful as a fuel and fuel oil containing a petroleum component and a component of a biological origin

ABSTRACT

The invention relates to a hydrocarbon composition, which can be used as a fuel and/or fuel oil, containing a petroleum component (A) and a component of a biological origin (B), wherein the component of a biological origin is present in a quantity of up to 75% by volume with respect to the total composition. Said component of a biological origin (B) is prepared starting from a mix of a biological origin (C) containing esters of fatty acids, with possible aliquots of free fatty acids, by means of a process which comprises the following steps: 1) hydrodeoxygenation of the mix of a biological origin; 2) hydroisomerization of the mix resulting from step (1), after possible water and gas flow separation, wherein said hydroisomerization is preferably carried out in the presence of a catalytic system comprising: a) a carrier of an acidic nature, comprising a completely amorphous micro-mesoporous silica-alumina, with a SiO 2 /Al 2 O 3  molar ratio ranging from 30 to 500, a surface area larger than 500 m2/g, a pore volume ranging from 0.3 to 1.3 ml/g, an average pore diameter smaller than 40 A, b) a metal component containing one or more metals of group VIII, possibly mixed with one or more metals of group VIB.

The present invention relates to a diesel composition, its preparation,its use and the use of a particular component for a new purpose.

The addition of alkyl esters of fatty acids to diesel fuel compositions,with the aim of reducing the environmental impact deriving from the useof conventional fuels of an oil origin, is known. The addition of theseproducts of a biological origin can, on the other hand, cause a loss ofquality of the resulting mix, due to the fact that these products haveworse properties from the point of view of cold behaviour with respectto diesel fuel of an oil origin, and also to the fact that thesecompounds cause problems of instability due to the presence ofunsaturations.

A diesel composition is described in EP 1674552, containing a dieselbase and an alkyl ester of palm oil (POAE) wherein the addition of thealkyl ester, in a final concentration of 25% v/v with respect to thefinal mix, confers better characteristics to the resulting compositionwith respect to the starting diesel base from the point of view of coldbehaviour, with reference, in particular, to the CFPP parameter (coldfilter plugging point) which is diminished by the presence of POAE.

It has now been unexpectedly found that, by mixing, in particularproportions, diesel fuels of an oil origin with components of abiological origin prepared by subjecting mixtures of biological origins,containing esters of fatty acids, to a hydrodeoxygenation andhydroisomerization treatment, a hydrocarbon composition is obtained,characterized by unexpected improvements from the point of view of coldbehaviour, with respect to its components considered individually. Theseimprovements do not only relate to the CFPP value, but, even moreunexpectedly, they relate to the Cloud Point and Pour Point and areaccompanied by improvements in the cetane number and density decreases.

In Italian patent application MI 2006A002193, filed on Nov. 15, 2006,the Applicant described a process for the production of hydrocarbonfractions useful as diesel fuel, starting from a mixture of a biologicalorigin containing esters of fatty acids, possibly with aliquots of freefatty acids, by means of a process comprising the following steps:

-   -   1) hydrodeoxygenation of the mix of a biological origin;    -   2) hydroisomerization of the mix resulting from step (1), after        possible water and gas flow separation, wherein said        hydroisomerization is preferably carried out in the presence of        a catalytic system comprising:        -   a. a carrier of an acidic nature, comprising a completely            amorphous micro-mesoporous silica-alumina, with a SiO₂/Al₂O₃            molar ratio ranging from 30 to 500, a surface area larger            than 500 m²/g, a pore volume ranging from 0.3 to 1.3 ml/g,            an average pore diameter smaller than 40 Å,        -   b. a metal component containing one or more metals of group            VIII, possibly mixed with one or more metals of group VIB.

A particularly preferred aspect of the present invention relates to theuse of hydrocarbon fractions thus prepared as component of a biologicalorigin of the hydrocarbon compositions of the present invention: saidfractions allow the best improvements to be obtained as far as coldbehaviour of the resulting composition is concerned, with respect to itscomponents considered individually, both with reference to the CFPPvalue and the Cloud Point and Pour Point values. At the same time,improvements are obtained relating to the cetane number and decrease indensity.

An object of the present invention therefore relates to a hydrocarboncomposition containing an oil component (A) and a component of abiological origin (B), wherein said component (B) is present in aquantity which can reach 75% by weight with respect to the totalcomposition and wherein said component (B) is prepared starting from amixture of a biological origin (C) containing esters of fatty acids,with possible aliquots of free fatty acids, by means of a processcomprising the following steps:

-   -   1) hydrodeoxygenation of the mix of a biological origin;    -   2) hydroisomerization of the mix resulting from step (1), after        possible water and gas flow separation, wherein said        hydroisomerization is preferably carried out in the presence of        a catalytic system comprising:        -   a. a carrier of an acidic nature, comprising a completely            amorphous micro-mesoporous silica-alumina, with a SiO₂/Al₂O₃            molar ratio ranging from 30 to 500, a surface area larger            than 500 m²/g, a pore volume ranging from 0.3 to 1.3 ml/g,            an average pore diameter smaller than 40 Å,        -   b. a metal component containing one or more metals of group            VIII, possibly mixed with one or more metals of group VIB.

The compositions thus obtained can be suitably used as diesel fuel forengines and gas oil for heating systems.

The compositions can contain up to 75% by volume of the component of abiological origin (B) with respect to the total volume of thecomposition, even more preferably up to 40% by volume. Even a fewpercentage units of the component of a biological origin (B) can enhancethe cold properties of the resulting mixture with respect to the singlecomponents. Generally speaking, the amount of biological component (B)will be regulated according to the amount of oil component (A), in termsof density and cold properties, in accordance with the qualitativeconstraints of a fuel.

The component of a biological origin (B) used in the hydrocarboncomposition of the present invention, is preferably characterized by adensity ranging from 750 to 800 kg/m³; a viscosity ranging from 2,00 to4,00 cSt; a cloud point ranging from −20 to +5° C.; a sulphur contentlower than 3 mg/kg; a nitrogen content lower than 3 mg/kg; a watercontent lower than 50 mg/kg; an acidity lower than 0.1 mg KOH/g; aboiling range of 240 to 300° C. expressed as a boiling point of 10% byvolume and 90% by volume in ASTM D86. The CFPP of the component of abiological origin preferably ranges from −25 to +5° C. The components ofa biological origin (B) are prepared by means of the process comprisinga hydrodeoxygenation step and a hydroisomerization step, from mixturesof biological origins (C) containing esters of fatty acids, withpossible aliquots of free fatty acids, wherein said mixtures (C) can beof a vegetable or animal origin. The amount of fatty acids in themixtures (C) can vary, for example, from 2 to 20% by weight with respectto the total mixture of a biological origin. Typically, the esters offatty acids contained in said mixtures (C) are triglycerides of fattyacids, wherein the hydrocarbon chain of the fatty acid can contain from12 to 24 carbon atoms and can be mono- or poly-unsaturated. The mixturesof a biological origin (C) can be selected from vegetable oils,vegetable fats, fish oils or mixtures thereof. Oils or vegetable fatscan be sunflower oils, rape oil, canola oil, palm oil, soybean, hemp,olive, linseed oil, charlock, peanuts, castor oil, coconut oil or fattyoils contained in pine wood (“tall oil”) or mixtures thereof. The animaloils or fats can be selected from lard, tallow, milk fats and mixturesthereof. Recycled oils and fats from the food industry can also be used,of both an animal and vegetable origin. The vegetable oils and fats canalso derive from selected plants, by genetic engineering.

As far as the petroleum components (A) are concerned, all the knowndiesel cuts can be used in the hydrocarbon compositions of the presentinvention; petroleum components deriving from the mixing of diesel cutsof different origins and compositions, are also suitable. The sulphurcontent of these diesel cuts preferably ranges from 2,000 to 50 mg/kg,even more preferably from 50 to 3 mg/kg.

Typical diesel cuts are medium distilled products, defined as oil cuts,preferably having a boiling point ranging from 180 to 380° C. Examplesof these cuts can be gas oils from primary distillation, gas oils fromvacuum distillation, thermal or catalytic cracking, such as, forexample, the desulphurized gas oil cut coming from fluid bed catalyticcracking (light cycle oil (LCO)), fuels coming from a Fischer-Tropschprocess or of a synthetic origin.

Cuts obtained from the above after hydrogenation treatment can also beused. By selecting the suitable component of a biological origin (B),the present invention generally also allows diesel cuts having very poorcp, cfpp, cetane number and density characteristics to be exploited forthe preparation of the new hydrocarbon compositions.

According to another aspect of the present invention, mixturescontaining one or more diesel cuts mixed with a desulphurized gas oilcoming from fluid bed catalytic cracking (LCO), can be used ascomponents of a petroleum origin (A). The hydrocarbon compositions ofthe present invention allow a low-value component to be upgraded as gasoil.

The diesel cuts used in the compositions of the present invention canhave a density ranging from 830 to 910 kg/m³ and a cetane number higherthan 25. The cuts which can be used normally have a CFPP ranging from +8to −15° C. Typically, these diesel cuts are those normally used as fuelsin diesel engines or as gas oil for heating.

The composition, object of the present invention, can also containadditives for improving the cold behaviour, detergents, additives forimproving the lubricity, anti-foam agents, cetane improvers, anti-rustagents, antioxidants, anti-wear agents, antistatic products. Theconcentration of each of these additives is preferably not higher than1% by weight.

The hydrocarbon composition of the present invention is characterized byimproved cold properties with respect to the same properties of thecorresponding components selected individually. In particular, thepresence of the biological component (B), even at low concentrations inthe order of only a few units percentage, is unexpectedly capable ofimproving not only the CFPP, but also the cloud point and pour point ofthe diesel fuel as such. By the addition of this biological component(B) and in relation to its quality, a CFPP improvement can be obtained,with respect to that of the single components, ranging from 1 to 8° C.compared with the value of the component of a petroleum origin as such.The CFPP is measured by using the EN 116 method and corresponds to thetemperature at which, and below which, the waxes contained in the fuelseparate, causing flow problems through a particular filter. The cloudpoint of the hydrocarbon compositions of the present invention can vary,with respect to that of the single components, with an improvement of 1to 6° C.

The cloud point is measured according to the method ASTM D2500.

The possibility of also using high amounts of the biological component(B) in the composition, is desirable from an environmental point of viewand, contemporaneously, can allow other advantages to be obtained inaddition to those already described, such as, for example, the necessityof using lower amounts of additives: for example, an improvement can beobtained in the cold and cetane properties without the use, or with theuse in lower quantities, of the relative additives.

The compositions of the present invention can be prepared by the directmixing of the components, preferably by means of mixing or incorporationof the component of a biological origin (B) in the component of apetroleum origin (A), in particular by the mixing or incorporation ofthe component (B) in the diesel cut or selected mix of diesel cuts.Possible further additives present in the final composition can beintroduced either in the final composition or in the diesel cut, or inthe component of a biological origin, before their mixing.

As far as the preparation of the biological component (B) used in thecomposition of the present invention is concerned, this includessubjecting a mixture of a biological origin (C), containing esters offatty acids, and possibly also free fatty acids, to a hydrodeoxygenationstep and an isomerization step, wherein the conditions for thehydrodeoxygenation and the hydroisomerization which can be used and therelative catalysts can all be products known to experts in the field.According to a preferred aspect, the hydrodeoxygenation step is carriedout as described in the co-pending Italian patent application MI2006A002193, whose paragraphs are provided hereunder and represent anintegral part of the description of the invention according to thepresent patent application.

As far as the hydroisomerization step is concerned, this can be suitablyeffected in the presence of hydrogen at a pressure varying from 25 to 70atm, and a temperature ranging from 250 to 450° C. Catalysts which canbe suitably used are those containing one or more metals of group VIII,possibly in a mixture with one or more metals of group VI, appropriatelysupported.

Carriers suitable for the purpose consist of one or more metal oxides,preferably alumina, silica, titania, zirconia, and mixtures thereof.These catalysts are typically prepared by impregnation of the oxidecarrier with a suitable salt solution of the metal(s). The impregnationis followed by a thermal treatment in a suitable atmosphere to decomposethe precursor salt and obtain the supported metal. It is possible toproceed with subsequent impregnations in order to reach the desiredmetal charge level and also to differentiate, in the event of severalmetals, the carriers of the same. Processes are also known for thepreparation of said catalysts instead of through impregnation, byprecipitation of the metal precursor from a saline solution of the samemetal on its carrier, or by co-precipitation of the various componentsof the catalyst, i.e. metal and carrier.

According to a particularly preferred aspect of the present invention,components of a biological origin (B) are used obtained by subjecting amixture of a biological origin (C) containing esters of fatty acids and,possibly, free fatty acids, to a process comprising a hydrodeoxygenationstep and an isomerization step, wherein a catalytic system is used inthe hydroisomerization step, comprising:

-   a) a carrier of an acidic nature, comprising a micro-mesoporous    silica-alumina completely amorphous, having a SiO₂/Al₂O₃ molar ratio    ranging from 30 to 500, a surface area larger than 500 m²/g, a pore    volume ranging from 0.3 to 1.3 ml/g, an average pore diameter    smaller than 40 Å.-   b) a metal component containing one or more metals of group VIII,    possibly mixed with one or more metals of group VIB.

These particular components (B) and the process for their preparation,are described in the co-pending Italian patent application MI2006A002193, filed on Nov. 15, 2006 in the name of the Applicant, whoseparagraphs are included hereunder to form an integral part of thedescription of the invention, according to the present patentapplication. The process described in Italian patent applicationMI2006A002193 allows hydrocarbon mixtures to be prepared, called, in thepresent application, components of a biological origin (B), by means ofthe hydrodeoxygenation of a mixture of a biological origin (C)containing esters of fatty acids, possibly with aliquots of free fattyacids, which can be vegetable oils such as sunflower oils, rape oil,canola oil, palm oil, or fatty oils contained in pine wood (“tall oil”),followed by hydroisomerization, which allows hydrocarbon mixtures to beobtained wherein the isoparaffin content can be higher than 80%, theremaining part being n-paraffins. In accordance with the above, saidprocess produces a hydrocarbon fraction which can be used as dieselfuel, starting from a mixture of a biological origin, containing estersof fatty acids, possibly also containing free fatty acids, and comprisesthe following steps:

-   1) hydrodeoxygenation of the mix of a biological origin;-   2) hydroisomerization of the mix resulting from step (1), after    possible water and gas flow separation, wherein said    hydroisomerization is preferably carried out in the presence of a    catalytic system comprising:    -   a) a carrier of an acidic nature, comprising a completely        amorphous micro-mesoporous silica-alumina, with a SiO₂/Al₂O₃        molar ratio ranging from 30 to 500, a surface area larger than        500 m²/g, a pore volume ranging from 0.3 to 1.3 ml/g, an average        pore diameter smaller than 40 Å,    -   b) a metal component containing one or more metals of group        VIII, possibly mixed with one or more metals of group VIE.

As already mentioned, the mixtures of a biological origin (C) used inthis preparation process, contain esters of fatty acids, possibly withaliquots of free fatty acids, and can be mixtures of an animal orvegetable origin. The aliquot of fatty acids can vary, for example, from2 to 20% by weight, with respect to the total mixture of a biologicalorigin. The esters of fatty acids contained in said mixtures aretypically triglycerides of fatty acids, wherein the hydrocarbon chain ofthe fatty acid can contain from 12 to 24 carbon atoms and can be mono-or poly-unsaturated. The mixtures of a biological origin can be selectedfrom vegetable oils, vegetable fats, animal fats, fish oils or mixturesthereof. The oils or vegetable fats can be sunflower oils, rape oil,canola oil, palm oil, soybean, hemp, olive, linseed oil, peanuts, castoroil, charlock oil, coconut oil or fatty oils contained in pine wood(“tall oil”) or mixtures thereof. The animal oils or fats can beselected from lard, tallow, milk fats and mixtures thereof. Recycledoils and fats from the food industry can also be used, of both an animalor vegetable origin. The vegetable oils and fats can also derive fromselected plants, by genetic engineering.

The mixtures of a biological origin (C), used in this preparationprocess, can also be mixed with other components before being fed to theprocess, for example, mixed with one or more hydrocarbons.

In the first step (step HDO) the mixture of a biological origin (C) ishydrodeoxygenated with hydrogen in the presence of a hydrodeoxygenationcatalyst.

In this step, the hydrogenation of the double bonds present in the esterchains of the triglycerides takes place, together with the cracking ofthe triglyceride structure and deoxygenation both throughdecarboxylation and hydrogenation with the formation of water.

All hydrogenation catalysts known in the art, containing one or moremetals selected from metals of group VIII and group VIB, suitablysupported, can be used. Carriers suitable for the purpose consist of oneor more metal oxides, preferably alumina, silica, titania, zirconia ormixtures thereof.

The metal or metals are preferably selected from Pd, Pt, Ni or from thepairs Ni—Mo, Ni—W, Co—Mo and Co—W, Ni—Mo and Co—Mo being preferred.These catalysts are typically prepared by means of impregnation of theoxidic carrier with a solution of a suitable salt of the metal ormetals. The impregnation is then followed by a thermal treatment, in asuitable atmosphere, to decompose the precursor salt and obtain thesupported metal. It is possible to proceed with subsequentimpregnations, in order to reach the desired level of metal charge andalso to differentiate their supporting, in the case of the presence ofvarious metals. Processes are also known for the production of thesecatalysts, instead of through impregnation, by precipitation of themetal precursor from a saline solution of the metal itself on thecarrier, or by co-precipitation of the various components of thecatalyst, i.e. of the metal and carrier.

Catalytic compositions can also be used such as Ni—Mo—P on zeolite,Pd/zeolite, Pt/MSA, wherein MSA is a silica-alumina having particularcharacteristic described in EP 340868, EP 659478, EP 812804, and used ascarrier also for the catalytic compositions used in the subsequenthydroisomerization step. Catalysts which can be suitably used in the HDOstep are described, for example, in J. T. Richardson, “Principal ofcatalyst development”, Plenum Press, New York, 1989, Chapter 6.

The catalysts of the type Ni—Mo, Ni—W, Co—Mo and Co—W preferablypreviously undergo sulphidation. The presulphidation procedure iseffected according to the known techniques.

In order to maintain the catalyst in sulphided form, the sulphidationagent, for example, dimethyl disulphide, is fed together with thefeedstock of a biological origin, after a possible purification step ofsaid feedstock, in a quantity ranging from 0.02 to 0.5% by weight(140-3400 ppm S).

Alternatively, the co-feeding can be effected of a “straight run” gasoil with a high S content (S>1%), in such a concentration as to reachthe same total amount of S in the feedstock.

The HDO reaction is carried out in a reaction zone comprising one ormore catalytic beds, in one or more reactors. According to a preferredaspect, it is effected in a typical fixed bed hydrotreating reactor. Thestream of hydrogen and feedstock of a biological origin can be sent inequicurrent or countercurrent. The reactor can have adiabatic catalyticbeds in a number higher than or equal to 2. As this is an exothermicreaction, with the production of heat, there will be a temperature risein each catalytic bed. By the feeding, between one catalytic bed andanother, of a stream of hydrogen and/or liquid feedstock at a definedtemperature, it is possible to obtain a constant or increasingtemperature profile. This operating procedure is normally indicated as“splitted feed”.

As an alternative to an adiabatic layer reactor, resort can be made to atube-bundle reactor. The catalyst is suitably charged inside the tubes,whereas a diathermic liquid (dowtherm oil) is sent to the mantle sidewith the aim of removing the reaction heat.

For a better regulation of the thermal profile in the reactor, whetherthis be with adiabatic layers or tube-bundle, the reactor itself can berun with the recirculation of a part of the effluents, according to thetypology known as recycling reactor. The function of the recycling is todilute the fresh feedstock in the reactor thus limiting the thermalpeaks due to the exothermicity of the reaction. The recycling ratio,i.e. the amount of recirculated fraction with respect to the freshfeedstock can vary from 0.5 to 5 w/w.

A further reactor configuration which can be used for this applicationis a slurry reactor in which the hydrodeoxygenation catalyst is suitablyformed in microspheres and dispersed in the reaction environment. Thegas-liquid-solid mixing in this case can be favoured by mechanicalstirring or by forced recirculation of the reaction fluids.

The HDO step is preferably carried out at a pressure varying from 25 to70 bar, preferably from 30 to 50 bar, and at a temperature ranging from240 to 450° C., preferably from 270 to 430° C. It is preferable tooperate with an LHSV ranging from 0.5 to 2 hours⁻¹, even more preferablyfrom 0.5 to 1 hours⁻¹. The H₂/mixture of a biological origin ratiopreferably ranges from 400 to 2,000 Nl/l.

Before the HDO step, the charge of a biological origin (C) can besuitably treated in order to remove the content of alkaline metals (forexample Na, K) and alkaline earth metals (for example Ca), possiblycontained in the feedstock. This pretreatment can be carried out byadsorption on a suitable material: for example the known percolationtechniques can be used on a column filled with acid earth or clays suchas for example montmorillonites, bentonites, smectites, acidicsepiolites. For this purpose, the products available on the market suchas Filtrol, Tonsil, Bentolites H and L, SAT-1, can be used.

Alternatively, ion exchange resins can be used, or slightly acidicwashings obtained for example by contact with sulphuric acid, nitricacid or hydrochloric acid, preferably at room temperature andatmospheric pressure.

The effluents of the HDO step (1) are preferably subjected topurification treatment before being sent to the subsequenthydroisomerization step. The purification treatment can comprise aseparation step and a washing step. According to this preferred aspect,the effluents of step (1) are sent to a high pressure gas-liquidseparator. A gaseous phase, essentially consisting of hydrogen, water,CO and CO₂ and light paraffins (C₄ ⁻), is recovered. NH₃, PH₃ and H₂Scan also be present in small quantities. After separation, the gaseousphase is cooled and the water (possibly containing traces of alcoholsand carboxylic acids) and condensable hydrocarbons are separated bycondensation. The remaining gaseous phase is purified to allow therecycling of hydrogen to the reaction step (1). Methods of the known artare adopted for the purification, by means of caustic washings, forexample with aqueous solutions of NaOH or Ca(OH)₂, or by means of thewell-known purification technique with amines (for example MEA,monoethanolamine, or DEA, diethanolamine). At the end of thepurification the CO₂, H₂S, PH₃ and NH₃ are removed and the gaseousfraction thus obtained essentially consists of H₂ with possible tracesof CO. In order to limit the accumulation of CO in the recycled gases,it can be removed by cuproammonia washing or by methanation, accordingto technologies known to experts in the field.

The liquid phase separated in the high pressure separator consists of ahydrocarbon fraction, essentially consisting of linear paraffins with anumber of carbon atoms varying from 14 to 21, prevalently from 15 to 19.Depending on the operating conditions of the separator, the liquidfraction can contain small quantities of H₂O and oxygenated compounds,such as for example alcohols and carbonyl compounds. The residual S canbe lower than 10 ppm. The liquid fraction can then be washed with agaseous hydrocarbon, for example CH₄, or nitrogen or hydrogen, in astripper, in order to further reduce the water content.

The resulting hydrocarbon mixture is fed to the subsequenthydroisomerization step (2). The hydroisomerization step is carried outin the presence of hydrogen and a catalytic composition which comprises:

a) a carrier of an acidic nature comprising a completely amorphousmicro-mesoporous silica-alumina having a SiO₂/Al₂O₃ molar ratio rangingfrom 30 to 500, a surface area greater than 500 m²/g, a pore volumeranging from 0.3 to 1.3 ml/g, an average pore diameter lower than 40 Å,

b) a metal component containing one or more metals of group VIII,possibly mixed with one or more metals of group VIB.

The carrier of an acidic nature (a) of the catalytic composition used inthe present invention comprises a silica-alumina preferably having aSiO₂/Al₂O₃ molar ratio ranging from 50 to 300.

According to a preferred aspect, the carrier of an acid nature (a)comprises a silica-alumina with a porosity ranging from 0.3 to 0.6 ml/g.

Completely amorphous micro-mesoporous silica-aluminas, which can be usedas carrier (a) of the catalytic compositions of the hydroisomerizationstep of the present invention, are described in U.S. Pat. No. 5,049,536,EP 659478, EP 812804, and called MSA. Their powder XRD pattern does nothave a crystalline structure and does not show any peak. U.S. Pat. No.5,049,536, EP 659478, EP 812804 also describe various methods forpreparing silica-aluminas suitable as carrier (a). Silica-aluminas whichcan be used for example for the process of the present invention can beprepared, in accordance with EP 659478, starting fromtetra-alkylammonium hydroxide, an aluminium compound which can behydrolyzed to Al₂O₃, and a silicon compound which can be hydrolyzed toSiO₂, wherein said tetra-alkylammonium hydroxide is atetra(C₂-C₅)alkylammonium hydroxide, said hydrolyzable aluminiumcompound is an aluminum tri(C₂-C₄)alkoxide and said hydrolysable siliconcompound is a tetra (C₁-C₅) alkylorthosilicate: these reagents aresubjected to hydrolysis and gelification operating at a temperatureequal to or higher than the boiling point, at atmospheric pressure, ofany alcohol which is developed as by-product of said hydrolysisreaction, without the elimination or substantial elimination of saidalcohols from the reaction environment. The gel thus produced is driedand calcined, preferably in an oxidizing atmosphere at a temperatureranging from 500 to 700° C., for a period of 6-10 hours. It ispreferable to operate by preparing an aqueous solution of thetetra-alkylammonium hydroxide and aluminium trialkoxide and thetetra-alkylorthosilicate is added to said aqueous solution, operating ata temperature lower than the hydrolysis temperature, with a quantity ofthe reagents which is such as to respect the SiO₂/Al₂O₃ molar ratio of30/1 to 500/1, the tetra-alkylammonium hydroxide/SiO₂ molar ratio of0.05/1 to 0.2/1 and H₂O/SiO₂ molar ratio of 5/1 to 40/1, the hydrolysisand gelification is caused by heating to a temperature higher thanapproximately 65° C. up to about 110° C., operating in an autoclave atthe autogenous pressure of the system, or at atmospheric pressure in areactor equipped with a condenser.

According to EP 812804, silica-aluminas which can be used as component(a) of the catalytic composition for the hydroisomerization step can beprepared by means of a process which comprises:

-   -   preparing a mixture starting from a tetra-alkylorthosilicate, a        C₃-C₆ alkyl alcohol or dialcohol, a tetra-alkylammonium        hydroxide having the formula R₁(R₂)₃NOH wherein R₁ is a C₃-C₇        alkyl and R₂ is a C₁ or C₃-C₇ alkyl, in the presence of a        hydrolysable aluminium compound, wherein the molar ratios fall        within the following ranges:        alcohol/SiO₂≦20

R₁(R₂)₃NOH/SiO₂=0.05-0.4 H₂O/SiO₂=1-40

Al₂O₃/SiO₂ greater than 0 and less than 0.02

-   -   subjecting said mixture to hydrolysis and subsequent        gelification at a temperature close to the boiling point of the        alcohol or mixture of alcohols present;    -   subjecting the gel obtained to drying and calcination.

The carrier of an acidic nature (a) of the catalyst which is used in theprocess of the present invention can be in the form of an extrudedproduct containing traditional binders, such as for example aluminiumoxide, bohemite or pseudobohemite. The extruded product can be preparedaccording to techniques well-known to experts in the field. Thesilica-alumina and the binder can be premixed in weight ratios rangingfrom 30:70 to 90:10, preferably from 50:50 to 70:30. At the end of themixing, the product obtained is consolidated into the desired end-form,for example extruded pellets or tablets. According to a preferredembodiment the methods and binders described in EP 550922 and EP 665055can be used, the latter being preferred, whose contents are incorporatedherein as reference.

A typical preparation method of the component of an acidic nature (a) inthe form of an extruded product (EP 665055) comprises the followingsteps:

(A) preparing an aqueous solution of a tetra-alkylammonium hydroxide(TAA-OH), a soluble aluminium compound capable of hydrolyzing in Al₂O₃and a silicon compound capable of hydrolyzing to SiO₂, in the followingmolar ratios:SiO₂/Al₂O₃ from 30/1 to 500/1TAA-OH/SiO₂ from 0.05/1 to 0.2/1H₂O/SiO₂ from 5/1 to 40/1(B) heating the solution thus obtained to cause its hydrolysis andgelification and obtain a mixture A with a viscosity ranging from 0.01to 100 Pa sec;(C) adding to the mixture A, first a binder belonging to the group ofbohemites or pseudo-bohemites, in a weight ratio with the mixture Aranging from 0.05 to 0.5, and subsequently a mineral or organic acid ina quantity ranging from 0.5 to 8.0 g per 100 g of binder;(D) heating the mixture obtained under point (C) to a temperatureranging from 40 to 90° C., until a homogeneous paste is obtained, whichis subjected to extrusion and granulation;(E) drying and calcining the extruded product in an oxidizingatmosphere.

Plasticizing agents, such as methylcellulose, are preferably also addedin step (C) to favour the formation of a homogeneous and easilyprocessable paste.

In this way a granular acid carrier is obtained, preferably containing aquantity ranging from 30 to 70% by weight of inert inorganic binder, theremaining quantity consisting of amorphous silica-alumina essentiallyhaving the same characteristics with respect to porosity, surfaceextension and structure described above for the same silica-aluminawithout a binder.

With respect to the metals contained in the metallic component (b) ofthe catalytic compositions used in the hydroisomerization step of theprocess of the present invention, this is selected from metals of groupVIII, optionally mixed with one or more metals of group VIB.Compositions containing only metals of group VIII are preferred. Themetal or metals of group VIII are preferably selected from Pt, Pd, Niand Co. In particular, when the metallic component contains only metalsof group VIII, the metal or metals are preferably selected from Pt, Pdand Ni. When the metallic component contains both one or more metals ofgroup VIII and one or more metals of group VIB, the metal of group VIIIis preferably selected from Ni and Co. The metal of group VIB ispreferably selected from Mo and W.

The metal of group VIII is preferably in a quantity ranging from 0.1 to5% by weight with respect to the total weight of the catalyticcomposition. The metal of group VIB, when present, is in a quantityranging from 1 to 50, even more preferably in a quantity ranging from 5to 35% by weight with respect to the total weight of the catalyticcomposition. The weight percentage of the metal, or metals, refers tothe metal content expressed as a metal element; in the final catalyst,after calcination, said metal is in the form of an oxide.

The metals of group VIII, and optionally group VI, contained in thecatalytic composition used in the hydroisomerization step (2) can bedeposited onto the carrier (a) with all the techniques known to expertsin the field. Catalytic compositions which can be well used in thehydroisomerization step of the present invention containing one or moremetals of group VIII, and their preparations, are described in EP582347, EP 1101813 and WO 2005/103207.

In particular, EP 582347 describes catalytic compositions, which can beused in the hydroisomerization of n-paraffins, containing one or moremetals of group VIII and a carrier of silica gel and alumina amorphousto X-rays, with a SiO₂/Al₂O₃ molar ratio ranging from 30 to 500, asurface area within the range of 500 to 1000 m²/g, a pore volume rangingfrom 0.3 to 0.6 ml/g and a pore diameter prevalently within the range of10 to 30 Å. EP 1101813 describes catalytic compositions, which can beused for the preparation of medium distillates, containing one or moremetals of group VIII and a carrier of silica gel and calcined alumina,amorphous to X-rays, with a SiO₂/Al₂O₃ molar ratio ranging from 30 to500, a surface area within the range of 500 to 1000 m²/g, a pore volumeranging from 0.2 to 0.8 ml/g and an average pore diameter within therange of 10 to 40 Å.

WO 2005/103207 describes catalytic compositions which can be used forthe upgrading of distillates, containing one or more metals selectedfrom Pt, Pd, Ir, Ru, Rh and Re and a silica-alumina carrier, amorphousto X-rays, with a SiO₂/Al₂O₃ molar ratio ranging from 30 to 500, asurface area greater than 500 m²/g, a pore volume ranging from 0.3 to1.3 ml/g and an average pore diameter less than 40 Å.

In general, in the compositions used in the hydroisomerization step (2),containing only the metal of group VIII, the metal, according to thepreparations described in the patents indicated above, can be introducedby means of impregnation or ion exchange. According to the firsttechnique, the component of an acidic nature (a), also in extruded form,and preferably in the extruded form prepared according to the processdescribed in EP 665055, is wet with an aqueous solution of a compound ofthe metal of group VIII, operating for example at room temperature, andat a pH ranging from 1 to 4. The aqueous solution preferably has aconcentration of metal expressed as g/l ranging from 0.2 to 2.0. Theresulting product is dried, preferably in air, at room temperature, andis calcined in an oxidizing atmosphere at a temperature ranging from 200to 600° C.

In the case of alcohol impregnation, the acid component (a), also inextruded form, and preferably in the extruded form prepared according tothe process described in EP 665055, is suspended in an alcohol solutioncontaining the metal. After impregnation the solid is dried andcalcined.

According to the ion exchange technique, the acid component (a), also inextruded form, and preferably in the extruded form prepared according tothe process described in EP 665055, is suspended in an aqueous solutionof a complex or salt of the metal, operating at room temperature and apH ranging from 6 to 10. After the ion exchange, the solid is separated,washed with water, dried and finally thermally treated in an inert andoxidizing atmosphere. Temperatures which can be used for the purpose arethose ranging from 200 to 600° C.

Compounds of metals which can be well used in the preparations describedabove are: H₂PtCl₆, Pt(NH₃)₄(OH)₂, Pt (NH₃)₄Cl₂, Pd (NH₃)₄ (OH)₂, PdCl₂,(CH₃COO)₂Ni, (CH₃COO)₂Co. When the catalytic composition comprises morethan one metal of group VIII the impregnation is carried out as follows:the acidic component (a), also in extruded form, and preferably in theextruded form prepared according to the process described in EP665055,is wet with a solution of a compound of a first metal, the resultingproduct is dried, it is optionally calcined, and is impregnated with asolution of a compound of a second metal. The product is dried and isthen calcined in an oxidizing atmosphere at a temperature ranging from200 to 600° C. Alternatively a single aqueous solution containing two ormore compounds of different metals can be used for contemporaneouslyintroducing said metals.

Before being used, the catalyst is activated by the known techniques,for example by means of a reduction treatment, and preferably by meansof drying and subsequent reduction. The drying is effected in an inertatmosphere at temperatures ranging from 25 to 100° C., whereas thereduction is obtained by thermal treatment of the catalyst in a reducingatmosphere (H₂) at a temperature ranging from 300 to 450° C., and apressure preferably ranging from 1 to 50 bar. Catalytic compositionswhich can be well used in the hydroisomerization step of the presentinvention containing one or more metals of group VIII and additionallyone or more metals of group VIB, and their preparations, are describedin EP 908231 and EP 1050571. In particular, EP 908231 describescatalytic compositions containing a mixture of metals belonging togroups VIB and VIII and a carrier of silica gel and alumina amorphous toX-rays, with a SiO₂/Al₂O₃ molar ratio ranging from 30 to 500, a surfacearea within the range of 500 to 1000 m²/g, a pore volume ranging from0.3 to 0.6 ml/g and an average pore diameter within the range of 10 to40 Å. When the hydroisomerization catalyst also contains a metal ofgroup VIB in the metal phase (b), the catalyst can be prepared by meansof aqueous or alcohol impregnation. More specifically, according to afirst technique, the silica-alumina, also in extruded form, andpreferably in the extruded form prepared according to the processdescribed in EP 665055, is wet with an aqueous solution of a compound ofthe desired metal of group VIB, operating at room temperature or atemperature close to room temperature. After aqueous impregnation, thesolid is dried and then a new impregnation is effected with an aqueoussolution of a compound of the desired metal of group VIII. After aqueousimpregnation, the solid is dried again and thermally treated in anoxidizing atmosphere. Suitable temperatures for this thermal treatmentrange from 200 to 600° C. The aqueous impregnation of the metallic phasecan also be effected in a single step, wherein the silica-alumina-basedacidic carrier is wet with a single aqueous solution containing both ofthe metal compounds of groups VIB and VIII, subsequently proceeding withthe same operating procedures described above. In the alcoholimpregnation technique, the silica-alumina, also in extruded form, andpreferably in the extruded form prepared according to the processdescribed in EP 665055, is suspended in an alcohol solution of acompound of a metal of group VIB and a compound of a metal of groupVIII, operating at room temperature or a value close to roomtemperature. After impregnation the solid is dried, preferably in air,at a temperature of about 100° C. and thermally treated in an oxidizingatmosphere, preferably in air.

The final hydroisomerization catalyst can be formulated and formed inextruded products having different forms (for example cylindrical,trilobated, etc.) as described for example in EP 1101813.

The catalytic compositions used in the hydroisomerization step of thepresent invention have the characteristic of being resistant to water: awater-inhibiting effect can be observed on the catalytic activity whichcan be recuperated however by increasing the temperature, whereas noirreversible deactivation was detected. An increase of a few ° C., from3 to 5, is typically sufficient for recovering the fall in activitycaused by 1000-2000 ppm of H₂O in the hydrocarbon charge. It ispreferable to operate with a water content around 1000 ppm, even morepreferably at a level lower than 300 ppm.

The reactor configuration for the hydroisomerization step is a fixed bedreactor. The thermal control in this case is not critical as thereaction is slightly exothermic. For this reason an adiabatic layerreactor is suitable. In any case, a tube bundle reactor can also beused.

The liquid charge deriving from the hydrodeoxygenation step can be sentinto the reactor in equicurrent or in counter current with respect tothe hydrogen. The counter current procedure is preferred when the liquidcharge contains a significant level of water and/or oxygenated compoundsnot converted in the first step of the process (>300 ppm of oxygen).

The water present, or formed by the oxygenated compounds during thehydroisomerization, is therefore removed in gaseous phase in the firstpart of the catalytic bed, thus reducing the contact time with the restof the catalyst. A particularly preferred arrangement for this catalyticstep is a reactor with a number of layers greater than or equal to 2, inwhich the first layer covered by the liquid hydrocarbon stream derivingfrom the hydrodeoxygenation step, therefore corresponding to the lastlayer covered by the gaseous hydrogen stream, consists not of thecatalyst, but of a filler of structures of inert material, for exampleceramic or stainless steel, or pellets or spherules of inert material,such as pumice, alpha-alumina, glass. The role of the filler is tofavour the gas-liquid contact, as the hydrocarbon charge to beisomerized will encounter the gaseous hydrogen stream before flowingonto the catalytic bed, thus being further anhydrified.

The hydroisomerization can be effected at a temperature ranging from 250to 450° C., preferably from 280 to 380° C., and at a pressure rangingfrom 25 to 70 bar, preferably from 30 to 50 bar. It is preferable tooperate at an LHSV ranging from 0.5 to 2 hours⁻¹. The H₂/HC ratiopreferably ranges from 200 to 1000 Nl/l.

The reaction conditions can be suitably selected to obtain a productwhose characteristics are balanced in relation to the cold properties ofthe diesel cut, with which the hydroisomerization product issubsequently mixed to prepare the hydrocarbon compositions of thepresent invention.

The mixture resulting from the hydroisomerization step is subjected todistillation to obtain a purified hydrocarbon mixture which can be usedas diesel fuel, which is used as component of a biological origin (B) inthe new hydrocarbon compositions of the present invention, havingimproved cold properties.

FIG. 1 illustrates a plant scheme which can be used in the process ofthe present invention for producing hydrocarbon fractions which can beused as diesel fuel, starting from a mixture of a biological origin (C)(biological mixture) containing esters of fatty acids and optionallyamounts of free fatty acids. The scheme of FIG. 1 is in accordance withwhat is described above in relation to the hydrodeoxygenation (DEOXreactor), purification by means of a high pressure separator and washing(SEP) and hydroisomerization (ISOM reactor) steps. In the scheme, afterthe hydroisomerization reactor, there are also the subsequent separationsteps, by means of a separator and distiller, to isolate the gas oilobtained. The dashed line represents a possible recycling of theeffluent deriving from the first step.

Some practical embodiment examples of the process object of the presentinvention are provided for a more detailed description for purelyillustrative purposes of particular aspects of the invention, whichhowever can in no way be considered as limiting the overall scope of theinvention itself.

EXAMPLE 1 Preparation of the Catalyst Pt/MSA Reagents and Materials

The following commercial reagents were used in the preparation describedhereunder:

tetrapropylammonium hydroxide (TPA-OH) SACHEM aluminium tri-isopropoxideFLUKA tetra-ethylsilicate DYNAMIT NOBEL alumina (VERSAL 250,Pseudo-Boehmite) LAROCHE methylcellulose (METHOCEL) FLUKA

The reagents and/or solvents used and not indicated above are those mostwidely used and can be easily found at normal commercial operatorsspecialized in the field.

PREPARATIVE EXAMPLES (i) Preparation of the Silica-Alumina Gel

A 100 litre reactor was preliminarily washed with 75 litres of asolution at 1% by weight of tetrapropylammonium hydroxide (TPA-OH) indemineralised water, maintaining the liquid under stirring for 6 hoursat 120° C. The washing solution is discharged and 23.5 litres ofdemineralised water, 19.6 kg of an aqueous solution at 14.4% by weightof TPA-OH (13.8 moles) and 600 g of aluminium tri-isopropoxide (2.94moles) are introduced. The mixture is heated to 60° C. and kept understirring at this temperature for 1 hour, in order to obtain a limpidsolution. The temperature of the solution is then brought to 90° C. and31.1 kg of tetra-ethylsilicate (149 moles) are rapidly added. Thereactor is closed and the stirring rate is regulated to about 1.2 m/s,maintaining the mixture under stirring for three hours at a temperatureranging from 80 to 90° C., with thermostat-regulated control to removethe heat produced by the hydrolysis reaction. The pressure in thereactor rises to about 0.2 MPag. At the end, the reaction mixture isdischarged and cooled to room temperature, obtaining a homogeneous andrelatively fluid gel (viscosity 0.011 Paas) having the followingcomposition molar ratios:

SiO₂/Al₂O₃=101 TPA-OH/SiO₂=0.093 H₂O/SiO₂=21 ii) Preparation of theExtruded Product

1150 g of alumina (VERSAL 150), previously dried for 3 hours in air at150° C., and 190 g of methylcellulose, are charged into a 10 litreplough mixer, maintained at a stirring rate of 70-80 revs per minute. 5kg of the silica-alumina gel prepared as described above and left torest for about 20 hours are then added over a period of time of about 15minutes, and the mixture is left under stirring for about 1 hour. 6 g ofglacial acetic acid are added and the temperature of the mixer isbrought to about 60° C., subsequently continuing the stirring until ahomogeneous paste is obtained, having the desired consistency for thesubsequent extrusion.

The homogenous paste obtained as described above is charged into a HUTTextruder, extruded and cut into pellets having the desired size (about2×4 mm). The product is left to rest for about 6-8 hours and then driedmaintaining it in a stream of air at 100° C. for 5 hours. It is finallycalcined in a muffle at 550° C. for 3 hours in a flow of nitrogen andfor a further 8 hours in air.

A porous solid with acid characteristics is thus obtained, essentiallyconsisting of silica/alumina (yield 95% with respect to the respectiveinitial reagents), having a BET of 608 m²/g.

iii) Impregnation of the Carrier with Platinum

12.1 ml of an aqueous solution of hydrochloric acid 0.6 M containing 4.5g/l of hexachloroplatinic acid (H₂PtCl₆, 0.133 mmoles) are dripped underslow stirring into a glass recipient containing 10 g of the porous solidprepared as described above. The mixture thus obtained is left understirring for 16 hours at room temperature. The water is then evaporatedat 60° C. in a stream of air, over a period of about 1 hour. The solidobtained is then dried maintaining it at 150° C. for two hours, andcalcined by heating in a muffle, in a stream of air, from roomtemperature to 500° C. over a period of three hours. At the end, asupported catalyst is obtained, which is used in the hydroisomerizationstep described in example 3 below, having the following characteristics:

59.8% by weight of amorphous silica-alumina (SiO₂/Al₂O₃ molar ratio=102)39.9% by weight of alumina (pseudo-bohemite)0.3% by weight of platinumPore volume: 0.6 ml/gBET: 600 m²/gCrushing strength: 10 kg/cm (radial); 90 kg/cm² (axial)

EXAMPLE 2 Hydrodeoxygenation Step (HDO)

The experimentation is carried out in a continuous reactor fed with soyaoil having the characteristics indicated in Table 1 (refined soya oilSipral) or palm oil having the characteristics shown in table 1.

The vegetable oil is fed to the first step with hydrogen in equicurrentin the presence of the commercial hydrogenation catalyst UOP UF 210based on NiMo/Al₂O₃ in sulphide form. The sulphidation of the catalystis effected in situ using gas oil containing dimethyldisulphide (DMDS)in a concentration which progressively varies from 3 to 9% by weight, ata temperature progressively varying within the range of 230 to 370° C.and a pressure of 70 bar, with a H₂/gas oil ratio of 1300 Nl/l and LHSVof 0.8 hours⁻¹. The vegetable oil is fed to the reactor in the presenceof a small quantity of DMDS (0.025%) to keep the catalyst in sulphideform.

The feedstock and hydrogen flow into the reactor in a descending mode.

The operating conditions used are the following:

-   -   Average temperature: 340-350° C.    -   LHSV: 1 hour⁻¹    -   Pressure: 35 bar    -   H₂/oil: 1500 Nl/l

TABLE 1 Refined Soya Oil Refined Palm Oil Palmatic acid %* (C16-0) 13.0641.41 Stearic acid %* (C18-0) 0.84 2.55 Oleic acid %* (C18-1) 27.0942.17 Linoleic acid %* (C18-2) 53.63 8.21 Linolenic acid %* (C18-3) 5.113.51 Arachidic acid % (C20-0) 0.07 0.07 Acidity (mgKOH/g) 0.11 1.2 H₂O(ppm) 2200 600 Na (ppm) 0.3 2.6 K (ppm) 0.3 0.6 Ca (ppm) 0.3 0.6 Mg(ppm) 0.1 0.1 Al (ppm) <0.1 <0.1 P (ppm) 0.65 0.25 Fe (ppm) <0.1 0.2 Cu(ppm) <0.1 <0.1 *The first number in brackets indicates the carbonatoms, the second the unsaturations.

The effluent product is separated in a gas/liquid separator from thegaseous fraction consisting of H₂, CO/CO₂ and light hydrocarbons almosttotally consisting of C₃H₈.

The liquid product, after the separation of water, consists ofn-paraffins, whose characteristics and distribution are indicated inTable 2 below.

TABLE 2 Hydrodeoxyg. Hydrodeoxyg. 5 from soya oil from palm oil Density(g/ml) 0.7916 0.7848 Carbon (% w/w) 84.64 84.96 Hydrogen (% w/w) 14.8314.92 Nitrogen (ppm) <1 <1 Sulphur (ppm) 3 <1 Oxygen (by difference, %)0.5 0.12 H₂O (after anhydrification, ppm) 100 20 Mono aromatic compounds(%) 2.9 0.2 Di aromatic compounds (%) 0.5 <0.1 Tri aromatic compounds(%) 0.1 <0.1 Total aromatic compounds (%) 3.5 0.2 Cloud point 21 19Gasoline in the feedstock (180° C., %) 0 0 Gas oil in the feedstock 9699 (180-380° C., %) Heavy products in the feedstock 5 2 (340+° C., %)Heavy products in the feedstock 4 1 (380+° C., %) Simulated distillation(ASTM D2887) Initial boiling point, ° C. 173 235  2% 269 270  5% 272 27110% 288 272 50% 309 303 90% 324 320 95% 351 320 98% 412 341 Finalboiling point, ° C. 462 422 Paraffin distribution (w %) totaln-paraffins 90.92 98.93 n-paraffins C11- 0.85 0.16 n-paraffins C12-C2087.7 98.47 n n-paraffins C20+ 2.4 0.3 Linear paraffin distribution(weight %) C14 0.19 0.7 C15 6.99 15.06 C16 4.32 27.19 C17 47.29 20.17C18 27.8 34.09 C19 0.64 0.32 C20 0.39 0.36

EXAMPLE 3 Hydroisomerization Step

The product obtained in the deoxygenation step described in example 2,containing 100 ppm of residual H₂O, is treated in equicurrent withhydrogen in the presence of the Pt/MSA catalyst prepared in the previousexample 1. The operating conditions used are indicated in Table 3

TABLE 3 Hydrodeoxygenated Hydrodeoxygenated product product from soyaoil from palm oil Temperature 345° C. 360° C. LHSV 2 hours⁻¹ 2 hours⁻¹Pressure 35 bar 35 bar H₂/HC 1000 NI/l 1000 NI/l catalyst ageing 200-300hours 1700-2000 hours

The effluent from the hydroisomerization reactor consists of a gaseousphase and a liquid phase, the two phases are separated in a gas/liquidseparator, the gaseous phase analyzed via GC consists of C₃/C₄ lightparaffins (LPG), whereas the liquid phase separated, containingparaffins with a number of carbon atoms ranging from 5 to 20, isanalyzed by means of GC to evaluate the isomerization degree, which,under these operating conditions is 70% for the product deriving fromthe soya oil and 80% for the product deriving from the palm oil, andused to evaluate the distillation curve.

The hydrocarbon product is then sent to a distillation column in orderto separate the gasoline fraction (10% by weight for the productderiving from the soya oil, 19.8 for the product deriving from the palmoil) from the diesel fraction (90% by weight for the product derivingfrom the soya oil, 81.2% by weight for the product deriving from thepalm oil). This latter fraction, containing paraffins with a number ofcarbon atoms ranging from 12 to 20, was characterized and the mainproperties are indicated in Table 4 below:

TABLE 4 Hydroisomer. Hydroisomer. Property Method from soya oil frompalm oil Density @ 15° C. ASTM D4052 783.9 777.7 (kg/m³) Sulphur (mg/kg)EN ISO 20846 <3 <3 Nitrogen (mg/kg) ASTM 4629 1 <0.3 Isoparaffin contentGaschromatog. 70 80 (w %) Total aromatic EN 12916 <1 <1 compounds Cloudpoint (° C.) ASTM D2500 −1.4 −15.2 Cold filter plugging EN 116 −5 −16point ° C. Pour point (° C.) ASTM D6892 −3 −15 Viscosity at 40° C. ASTMD445 3.093 2.627 (cSt) Acidity (mg KOH/g) ASTM 664 <0.1 <0.1 Brominenumber ISO 3829 <0.1 <0.1 Water (mg/kg) EN ISO 12937 30 10 Cetane numberEN ISO 5165 >76 >76 Cl4 EN ISO 4264 93 90 IQT pr EN 15195 84 —Distillation (° C.) ASTM D86 lbp 239 221 T5 262 238 T10 267 246 T20 274255 T30 279 262 T40 283 267 T50 285 271 T60 287 274 T70 289 277 T80 291280 T90 295 285 T95 300 289 Fbp 314 294

The fractions thus obtained are used in the following examples, ascomponents of a biological origin, for preparing hydrocarboncompositions in accordance with the present invention.

EXAMPLE 4

The diesel cuts used for preparing compositions according to the presentinvention, are listed and described in the following tables 5 and 6.

TABLE 5 Diesel cut mark Diesel cut description A desulphurized SR gasoil B industrial desulphurized gas oil at high density C industrialdesulphurized gas oil at low density D industrial gas oil includingcomponents from cracking E desulphurized LCO F 0.89 B + 0.11 E G 0.89C + 0.11 E H 0.89 D + 0.11 E I industrial gas oil, comparative tests

TABLE 6 Property Method A B C D E F G H I Density 15° C. ASTM 837.2827.1 841.4 843.5 909.6 836.2 849.1 850.9 842.7 (kg/m³) D4052 Sulphur ENISO 22 3 52 12 8 3 47 12 287 (mg/kg) 20846 Cloud point ASTM −2.9 −4.4−0.9 −0.8 −15.0 −6.9 −2.5 −2.1 −2.0 (° C.) D2500 Cold filter EN 116 −4−5 −2 −2 −15 −8 −4 −4 −3 plugging point (° C.) Pour point ASTM −3 −9 −3−6 −18 −12 −6 −6 (° C.) D6892 Viscosity at ASTM 3.522 3.193 3.746 3.1153.093 40° C. (cSt) D445 Cetane EN ISO 54.6 50.6 27.5 49.5 number 5165Cetane EN ISO 57.9 61.3 57.5 51.2 30.5 50.7 index 4264 Distillation ASTM(° C.) D86 lbp 210 205 189 202 198 180 T5 234 233 237 218 242 200 T10244 242 247 227 249 212 T20 257 253 261 239 258 T30 267 261 271 249 264244 T40 276 270 281 260 269 T50 284 279 291 270 275 274 T60 293 288 302282 281 T70 303 300 314 295 288 305 T80 315 314 329 311 297 T90 334 333347 334 312 343 T95 354 348 362 354 324 359 Fbp 367 356 370 370 336Tables 5 and 6 also describe the cut E, a desulphurized LCO cut which isused as such and mixed with diesel cuts, as components for preparinghydrocarbon compositions according to the present invention: inparticular cut F consists of 89% by volume of gas oil B and 11% byvolume of cut E, cut G consists of 89% by volume of cut C and 11% volumeof cut E, cut H consists of 89% by volume of cut D and 11% volume of cutE. The cuts shown in these tables are mixed with different volumepercentages of the components of a biological origin obtained fromexample 3.

Table 7 below indicates the characteristics of the cloud point (cp),cold filter plugging point (Cfpp), pour point (pp) and cetane number ofthe resulting hydrocarbon compositions.

In particular, the first column indicates the diesel cut used forpreparing the hydrocarbon composition, the second column indicates itsvolume concentration, with respect to the total volume, the third columnindicates the concentration of the component of a biological origin,according to example 3 and the fourth column indicates the origin of thecomponent of a biological origin:

TABLE 7 Diesel Vol. Fract.. Vol. Fract. Hydroisomer. cut diesel cuthydroisomer. oil oil origin cp CFPP pp NC 0 1 soya −1.4 −5 −3 >76 0 1palm −15.2 −16 −15 >76 A 1 0 −2.9 −4 −3 55 A 0.87 0.13 soya −3.9 −6 −658 A 0.81 0.19 soya −4.3 −8 −6 60 B 1 0 −4.4 −5 −9 B 0.90 0.10 soya −6.4−8 −9 B 0.5 0.5 soya −7.3 −11 −6 B 0.25 0.75 soya −5.3 −8 −3 C 1 0 −0.9−2 −3 C 0.9 0.1 soya −2.6 −5 −6 C 0.5 0.5 soya −6.4 −10 −6 C 0.25 0.75soya −4.9 −8 −3 D 1 0 −0.8 −2 −6 51 D 0.87 0.13 soya −2.1 −4 −6 55 D0.74 0.26 soya −3.1 −7 −6 56 D 0.50 0.50 soya −6.0 −10 −6 67 D 0.25 0.75soya −5.3 −9 −6 76 E 1 0 −15.0 −15 −18 E 0.25 0.75 palm −17.8 −21 −18 F1 0 −6.9 −8 −12 F 0.9 0.1 soya −7.4 −9 −9 G 1 0 −2.5 −4 −6 G 0.9 0.1soya −3.7 −6 −6 H 1 0 −2.1 −4 −6 H 0.9 0.1 soya −2.4 −5 −6

It is evident that the hydrocarbon compositions resulting from thecombination of the diesel cuts A, B, C, D and E with the component of abiological origin obtained in Example 3, have better characteristicswith respect to the cloud point and cfpp compared with the singlecomponent of the composition; also in the case of the pour point, thereis an analogous phenomenon, mainly with mixtures A and C. The sameimprovement is also found in the fuel compositions F, G and H, which arethe fuels B, C and D, respectively, enriched with LCO. As far as cetaneis concerned, as can be seen, this acts as an improver.

EXAMPLE 6

The following example shows the saving that can be obtained in terms ofquantity of Cfpp improver additive, when a sample of the diesel cut A ismixed with a component of a biological origin prepared according toexample 3. In particular, the table shows that the addition to cut A ofthe component of a biological origin from soya prepared in example 3, ina quantity increasing from 0.13 to 0.19 by volume, allows acorresponding decrease in the quantity of Cfpp improver necessary forobtaining a Cfpp of −12° C. The Cfpp improver is a commercial productbased on ethylene vinyl acetate (EVA) polymers.

TABLE 8 Diesel Hydroisomeriz. Diesel cut volume oil volume mg/kg Cutfraction fraction mg/kg additive Cfpp (° C.) −12° C. A 1 0 0 100 200 −4−9 −13 175 A 0.87 0.13 0 75 150 −6 −10 −14 113 A 0.87 0.19 0 75 150 −8−9 −14 120The first column indicates the volume fraction of fuel A, the secondcolumn the volume fraction of the hydrocarbon mixture from soya obtainedfrom example 3, the third column the quantity of improver used, thefourth column the corresponding Cfpp trend and the last column thequantity of improver necessary for obtaining a Cfpp of −12° C. inrelation to the hydrocarbon composition tested.

EXAMPLE 7 Comparative

A diesel composition according to EP 1674552 is prepared, by mixing gasoil of an industrial origin I, described in table 6, with a bio-dieselfrom palm oil, i.e. a methyl ester of palm oil (POME) having thecharacteristics shown in table 9.

TABLE 9 Property Method Density @ 15° C. (kg/m³) ASTM D4052 876.9Sulphur (mg/kg) EN ISO 20846 <3 Cloud point (° C.) ASTM D2500 12.0 Coldfilter plugging point ° C. EN 116 9 Pour point (° C.) ASTM D6892 13Viscosity at 40° C. (cSt) ASTM D445 4.510 Water (mg/kg) EN ISO 12937 290Cetane number EN ISO 5165 62 Cl4 EN ISO 4264 57 Distillation (° C.) ASTMD86 lbp 313 T5 322 T10 324 T30 326 T50 327 T70 330 T90 336 T95 346 Fbp347Table 10 indicates the characteristics of the blends of component I withPOME

TABLE 10 Diesel Diesel cut POME volume Cut volume fraction fraction Cp(° C.) Cfpp (° C.) 0 1 12.0 9 l 1 0 −2.0 −3 l 0.95 0.05 −1.0 −6 l 0.900.1 −0.7 −6 l 0.80 0.2 3.7 −1

It is evident that the resulting composition does not show anyimprovement in terms of cloud point (cp) with respect to the singlecomponents, and the improvement obtained on the Cfpp is to a lowerextent with respect to that which can be obtained with the compositionsof the present invention.

1) A hydrocarbon composition, containing a petroleum component (A) and acomponent of a biological origin (B), wherein said component (B) ispresent in a quantity of up to 75% by volume with respect the totalcomposition, and wherein said component (B) is prepared starting from amixture of a biological origin (C) containing esters of fatty acids,with possible aliquots of free fatty acids, by means of a processcomprising the following steps: 1) hydrodeoxygenation of the mixture ofa biological origin (C); 2) hydroisomerization of the mixture resultingfrom step (1), after possible water and gas flow separation. 2) Thecomposition according to claim 1, containing a petroleum component (A)and a component of a biological origin (B), wherein said component (B)is present in a quantity of up to 75% by volume with respect the totalcomposition, and wherein said component (B) is prepared starting from amixture of a biological origin (C) containing esters of fatty acids,with possible aliquots of free fatty acids, by means of a processincluding the following steps: 1) hydrodeoxygenation of the mixture of abiological origin (C); 2) hydroisomerization of the mixture resultingfrom step (1), after possible water and gas flow separation, saidhydroisomerization being effected in the presence of a catalytic systemcomprising: a. a carrier of an acidic nature, comprising a completelyamorphous micro-mesoporous silica-alumina, with a SiO₂/Al₂O₃ molar ratioranging from 30 to 500, a surface area greater than 500 m²/g, a porevolume ranging from 0.3 to 1.3 ml/g, an average pore diameter smallerthan 40 Å, b. a metal component containing one or more metals of groupVIII, possibly mixed with one or more metals of group VIB. 3) Thecomposition according to claim 1 or 2, wherein component (B) is presentin a quantity of up to 40% by volume with respect to the totalcomposition. 4) The composition according to claim 1 or 2, wherein thepetroleum component (A) is a diesel cut or a blend of diesel cuts. 5)The composition according to claim 4, wherein the diesel cut is selectedfrom medium distillates. 6) The composition according to claim 5,wherein the diesel cut is selected from distillates having a boilingpoint ranging from 180 to 380° C. 7) The composition according to claim4, 5 or 6, wherein the cuts are selected from gas oils from primarydistillation, gas oils from vacuum distillation and from thermal orcatalytic cracking, fuels coming from Fischer-Tropsch processes, fuelsof a synthetic origin and mixtures thereof. 8) The composition accordingto claim 7, wherein the diesel cut is a desulphurized gas oil comingfrom fluid bed catalytic cracking (LCO). 9) The composition according toone or more of the previous claims, wherein the petroleum component (A)is a hydrogenated diesel cut or a blend of hydrogenated diesel cuts. 10)The composition in accordance with one or more of the previous claims,wherein the petroleum component (A) comprises one or more diesel cuts inthe mixture with a desulphurized gas oil cut coming from fluid bedcatalytic cracking (LCO). 11) The composition according to claim 1 or 2,containing additives. 12) The composition according to claim 11,containing additives for improving the cold behaviour, anti-foamperformance, cetane number improvers, antirust agents, detergents,additives for improving the lubricity, anti-oxidant agents, anti-wearagents, antistatic agents. 13) The composition according to claim 1 or2, wherein the mixture of a biological origin (C) is a mixture of avegetable or animal origin. 14) The composition according to claim 1, 2or 13, wherein the esters of fatty acids, contained in the mixtures of abiological origin, are triglycerides of fatty acids, wherein thehydrocarbon chain of the fatty acid contains from 12 to 24 carbon atomsand is mono- or poly-unsaturated. 15) The composition according to claim14, wherein the mixture of a biological origin can be selected fromvegetable oils, vegetable fats, animal fats, fish oils or mixturesthereof. 16) The composition according to claim 15, wherein thevegetable oils or fats, possibly deriving from plants selected bygenetic engineering, are selected from sunflower oils, rape oil, canolaoil, palm oil, soybean, hemp, olive, linseed oil, charlock, peanuts,castor oil, coconut oil or fatty oils contained in pine wood (“talloil”) recycled oils and fats from the food industry and mixturesthereof, and animal oils or fats are selected from lard, tallow, milkfats, recycled oils or fats of the food industry and mixtures thereof.17) The composition according to claim 1 or 2, wherein the mixtures of abiological origin (C) are mixed with one or more hydrocarbons beforebeing fed to step (1). 18) The composition according to claim 1 or 2,wherein step (1) is effected in the presence of hydrogen and ahydrogenation catalyst containing a carrier and one or more metalsselected from the metals of groups VIII and VIB. 19) The compositionaccording to claim 18, wherein the carrier for the catalyst of step (1)is selected from alumina, silica, zirconia, titania or mixtures thereof.20) The composition according to claim 18, wherein the metal or metalscontained in the catalyst of step (1) are selected from Pd, Pt, Ni orfrom the pairs of metals Ni—Mo, Ni—W, Co—Mo and Co−W. 21) Thecomposition according to claim 18, wherein the catalyst of step (1) isselected from the catalytic compositions Ni—Mo—P on zeolite, Pd/Zeolite,Pt/MSA. 22) The composition according to claim 1, 2 or 18, wherein step(1) is carried out in a reaction zone comprising one or more catalyticbeds, in one or more reactors. 23) The composition according to claim22, wherein step (1) is carried out in a fixed-bed hydrotreatingreactor. 24) The composition according to claim 18, 22 or 23, wherein instep (1) the streams of hydrogen and feedstock of a biological origincan be sent in equicurrent or countercurrent. 25) The compositionaccording to claim 18, 22, 23 or 24, wherein the reactor has adiabaticlayers in a number higher than or equal to
 2. 26) The compositionaccording to claim 22, 23 or 25, wherein a stream of hydrogen and/orliquid feedstock, at a defined temperature, is sent between onecatalytic bed and another to obtain a constant or increasing temperatureprofile. 27) The composition according to claim 18 or 22, wherein thereactor is of the tube-bundle type, the catalyst is charged inside thetubes, and a diathermic liquid is sent into the mantle side. 28) Thecomposition according to claim 25 or 27, wherein the reactor is run withthe recirculation of part of the effluents. 29) The compositionaccording to claim 28, wherein the recycling ratio, i.e. the amount offraction recirculated with respect to the fresh feedstock, varies from0.5 to 5 by weight. 30) The composition according to claim 18, wherein aslurry reactor is used, in which the hydrodeoxygenation catalyst isformed as microspheres and dispersed in the reaction environment, andthe mixing is effected by mechanic stirring or by forced recirculationof the reaction fluids. 31) The composition according to claim 1 or 2,wherein step (1) is effected at a pressure varying from 25 to 70 bar, ata temperature ranging from 240 to 450° C. 32) The composition accordingto claim 31, wherein step (1) is carried out at a temperature rangingfrom 270 to 430° C. 33) The composition according to claim 31, whereinstep (1) is carried out at a pressure ranging from 30 to 50 bar. 34) Thecomposition according to claim 31, wherein step (1) is carried out at aLHSV ranging from 0.5 to 2 hr⁻¹. 35) The composition according to claim31, wherein step (1) is carried out with a H₂/mixture of a biologicalorigin ratio ranging from 400 to 2,000 Nl/l. 36) The compositionaccording to claim 18 or 20, wherein the catalysts based on Ni—Mo, Ni—W,Co—Mo and Co—W are sulphidated before being used. 37) The compositionaccording to claim 1 or 2, wherein the mixture of a biological origin issubjected to a pretreatment before being fed to step (1), wherein saidpretreatment is effected by means of adsorption, treatment with ionexchange resins or slightly acidic washings. 38) The compositionaccording to claim 1 or 2, wherein the mixture resulting from step (1)is subjected to purification treatment before being hydroisomerized,wherein the purification treatment comprises a separation step and awashing step. 39) The composition according to claim 38, wherein, in theseparation step, the mixture resulting from step (1) is sent to a highpressure gas-liquid separator, in order to recover a gaseous phase and aliquid phase. 40) The composition according to claim 39, wherein thegaseous phase, containing hydrogen, water, CO, CO₂, light paraffins(C4⁻) and possibly small amounts of NH₃, PH₃ and H₂₅, is cooled, waterand condensable hydrocarbons are separated by condensation, and theremaining gaseous phase is purified to obtain hydrogen which can berecycled to the reaction step (1). 41) The composition according toclaim 39, wherein the liquid phase separated in the high pressureseparator, formed by a hydrocarbon fraction, essentially consisting oflinear paraffins with a number of carbon atoms varying from 14 to 21, iswashed with hydrogen or nitrogen or a gaseous hydrocarbon, in astripper, before being fed to the subsequent hydroisomerization step(2). 42) The composition according to claim 1, wherein step (2) iscarried out in the presence of hydrogen and a catalytic systemcomprising one or more metals of Group VIII mixed with one or moremetals of Group VI. 43) The composition according to claim 2, whereinstep (2) is carried out in the presence of hydrogen and a catalyticcomposition which comprises: a) a carrier of an acidic nature comprisinga completely amorphous micro-mesoporous silica-alumina having aSiO₂/Al₂O₃ molar ratio ranging from 30 to 500, a surface area greaterthan 500 m²/g, a pore volume ranging from 0.3 to 1.3 ml/g, an averagepore diameter lower than 40 Å, b) a metal component containing one ormore metals of group VIII, possibly mixed with one or more metals ofgroup VIB. 44) The composition according to claim 2 or 43, wherein instep (2) the silica-alumina contained in the carrier of an acidic nature(a), has a SiO₂/Al₂O₃ molar ratio ranging from 50 to
 300. 45) Thecomposition according to claim 2 or 43, wherein in step (2) thesilica-alumina contained in the carrier of an acidic nature (a), has aporosity ranging from 0.3 to 0.6 ml/g 46) The composition according toclaim 2 or 43, wherein in step (2) the component of an acidic nature (a)of the catalytic system is in the form of an extruded product containinga binder. 47) The composition according to claim 46, wherein in step (2)the component of an acidic nature (a) of the catalytic system in theform of an extruded product containing a binder, is prepared by means ofa process comprising the following steps: (A) preparing an aqueoussolution of a tetra-alkylammonium hydroxide (TAA-OH), a solublealuminium compound capable of hydrolyzing into Al₂O₃ and a siliconcompound capable of hydrolyzing to SiO₂, in the following molar ratios:SiO₂/Al₂O₃ from 30/1 to 500/1 TAA-OH/SiO₂ from 0.05/1 to 0.2/1 H₂O/SiO₂from 5/1 to 40/1 (B) heating the solution thus obtained to cause itshydrolysis and gelification and obtain a mixture A with a viscosityranging from 0.01 to 100 Pa sec; (C) adding to the mixture A, first abinder belonging to the group of bohemites or pseudo-bohemites, in aweight ratio with the mixture A ranging from 0.05 to 0.5, andsubsequently a mineral or organic acid in a quantity ranging from 0.5 to8.0 g per 100 g of binder; (D) heating the mixture obtained under point(C), under stirring, to a temperature ranging from 40 to 90° C., until ahomogeneous paste is obtained, which is subjected to extrusion andgranulation; (E) drying and calcining the extruded product in anoxidizing atmosphere. 48) The composition according to claim 2, whereinin step (2) the catalytic system contains as metal component (b) one ormore metals of Group VIII selected from Pt, Pd, Ni, Co. 49) Thecomposition according to claim 48, wherein the catalytic system onlycontains metals of Group VIII and said metals are preferably selectedfrom Pt, Pd and Ni. 50) The composition according to claim 48, whereinthe catalytic system contains one or more metals of Group VIII and oneor more metals of Group VIB, said metals of group VIII are selectedbetween Ni and Co. 51) The composition according to claim 2, 48 or 50,wherein in step (2) the catalytic system contains as metal component (b)both one or more metals of group VIII and one or more metals of GroupVIB, and the metal of Group VIB is selected from Mo and W. 52) Thecomposition according to claim 2, wherein in the catalytic system ofstep (2) the metal of Group VIII is in a quantity ranging from 0.1 to 5%by weight with respect to the total weight of the catalyst. 53) Thecomposition according to claim 2, wherein in the catalytic system ofstep (2) the metal of Group VIB is in a quantity ranging from 1 to 50%by weight with respect to the total weight of the catalyst. 54) Thecomposition according to claim 53, wherein the metal of Group VIB is ina quantity ranging from 5 to 35% by weight. 55) The compositionaccording to claim 2, wherein in step (2) the catalytic system comprisesone or more metals of Group VIII and a carrier of silica gel andalumina, amorphous to X rays, having a SiO₂/Al₂O₃ molar ratio rangingfrom 30 to 500, a surface area in the range of 500 to 1000 m²/g, a porevolume ranging from 0.3 to 0.6 ml/g and a pore diameter mainly withinthe range of 10 to 30 Å. 56) The composition according to claim 2,wherein in step (2) the catalytic system comprises one or more metals ofGroup VIII and a calcined carrier of silica gel and alumina, amorphousto X rays, having a SiO₂/Al₂O₃ molar ratio ranging from 30 to 500, asurface area in the range of 500 to 1000 m²/g, a pore volume of up to0.8 ml/g and an average pore diameter within the range of 10 to 40 Å.57) The composition according to claim 2, wherein in step (2) thecatalytic system contains one or more metals selected from Pt, Pd, Ir,Ru, Rh and Re and a silica-alumina carrier, amorphous to X rays, havinga SiO₂/Al₂O₃ molar ratio ranging from 30 to 500, a surface area greaterthan 500 m²/g, a pore volume ranging from 0.3 to 1.3 ml/g and an averagepore diameter smaller than 40 Å. 58) The composition according to claim2, wherein in step (2) the catalytic system comprises a blend of metalsof Groups VIB and VIII and a carrier of silica gel and alumina,amorphous to X rays, having a SiO₂/Al₂O₃ molar ratio ranging from 30 to500, a surface area in the range of 500 to 1000 m²/g, a pore volumeranging from 0.3 to 0.6 ml/g and a pore diameter within the range of 10to 40 Å. 59) The composition according to claim 2, wherein thehydroisomerization step (2) is carried out in a fixed bed reactor. 60)The composition according to claim 59, wherein in step (2) the reactoris of the type with adiabatic layers. 61) The composition according toclaim 1, 59 or 60, wherein the mixture subjected to hydroisomerizationis fed to the reactor in equicurrent or countercurrent with respect tothe hydrogen. 62) The composition according to claim 61, wherein theprocess is effected in countercurrent, in a reactor with a number oflayers higher than or equal to 2, wherein the first layer, immersed bythe mixture subjected to hydroisomerization, consists of a fillerconsisting of inert material or pellets or spherules of inert material.63) The composition according to claim 1, wherein the hydroisomerizationstep (2) is carried out in the presence of hydrogen at a temperatureranging from 250 to 450° C. and a pressure ranging from 25 to 70 bar.64) The composition according to claim 2 or 43, wherein thehydroisomerization step (2) is carried out at a temperature ranging from250 to 450° C. and a pressure ranging from 25 to 70 bar. 65) Thecomposition according to claim 64, wherein step (2) is carried out at atemperature ranging from 280 to 380° C. 66) The composition according toclaim 64, wherein in step (2) the pressure ranges from 30 to 50 bar. 67)The composition according to claim 64, wherein step (2) is carried outwith a LHSV ranging from 0.5 to 2 hr⁻¹ and with a H₂/HC ratio of between200 and 1,000 hr⁻¹. 68) Use in a diesel composition, with the purpose ofimproving the cold properties, of a component of a biological origincontaining esters of fatty acids and possibly aliquots of free fattyacids, by means of a process including the following steps: 1)hydrodeoxygenation of the mixture of a biological origin; 2)hydroisomerization of the mixture resulting from step (1), afterpossible water and gaseous stream separation, and possible purificationtreatment. 69) Use in a diesel composition, with the purpose ofdecreasing the quantity of additives for improving the cold properties,of a component of a biological origin obtained from a mixture of abiological origin containing esters of free fatty acids, by means of aprocess comprising the following steps: 1) hydrodeoxygenation of themixture of a biological origin; 2) hydroisomerization of the mixtureresulting from step (1), after possible water and gaseous streamseparation, and possible purification treatment. 70) Use in a dieselcomposition, according to claim 68 or 69, of a component of a biologicalorigin obtained from a mixture of a biological origin, containing estersof fatty acids and possibly aliquots of free fatty acids, by means of aprocess including the following steps: 1) hydrodeoxygenation of themixture of a biological origin; 2) hydroisomerization of the mixtureresulting from step (1), after possible water and gaseous streamseparation, and possible purification treatment, said isomerizationbeing effected in the presence of a catalytic system comprising: a) acarrier of an acidic nature comprising a completely amorphousmicro-mesoporous silica-alumina having a SiO₂/Al₂O₃ molar ratio rangingfrom 30 to 500, a surface area greater than 500 m²/g, a pore volumeranging from 0.3 to 1.3 ml/g, an average pore diameter lower than 40 Å,b) a metal component containing one or more metals of Group VIII,possibly in a mixture with one or more metals of group VIB.